By means of local infusion at low concentrations and infusion volumes, or intraperitoenal injections of amphetamine and related compounds, significant changes in neuronal activity of neurons in the caudate-putamen and associated afferent projection systems will be sought. Similar experiments will be undertaken to determine how such alterations in neuronal activity following acute amphetamine administration are changed by long-term amphetamine for periods of from 1 to 5 weeks. Experiments will focus initially upon the nature of changes in neuronal activity following intraperitoneal administration of direct-acting dopamine agonists, such as apomorphine, and indirect dopamine agonists such as amphetamine. Later, such changes will be examined following long-term amphetamine pretreatment in rats. BIBLIOGRAPHIC REFERENCES: MacGregor, R., Miller, S.W., Groves, P. Slow rhythms and correlations in spike trains from midbrain neurons. Experimental Neurology, 1975, 47, 581-598: Parker, M., Miller, S.W., and Groves, P. Neuronal habituation and sensitization in the reticular formation of the rat. Physiological Psychology, 1975, 2, 464-470.